Apparatus for measuring in a continuous manner the oxygen in a molten metal

ABSTRACT

Apparatus for the continuous measurement by immersion of oxygen contained in a molten metal which includes solid oxygen electrolyte rod or strip; reference electrode having known oxygen potential; means for measuring the electrochemical potential present between the reference electrode and the metal which is to be tested; a protective tube surrounding the electrolyte; and wherein the electrolyte is held in the end of the tube by means of an oxide cement.

United States Patent 91 Richardson 111 3,719,574 1*March 6, 1973APPARATUS FOR MEASURING IN A CONTINUOUS MANNER THE OXYGEN IN A MOLTENMETAL [75] Inventor: Frederick Denys Richardson, Epsom, England [73]Assignees: Metallurgie Hoboken-Overpelt,

Brussels, Belgium; RST International Metals Limited, London, England;part interest to each Notice: The portion of the term of this patentsubsequent to May 9, 1989,

has been disclaimed.

[22] Filed: July 6, 1970 [21] App]. No.1 52,373

[52] US. Cl ..204/195 S [51] Int. Cl. ..G0ln 27/30 [58] Field of Search..204/195 S, l T; 324/29 [56] References Cited UNITED STATES PATENTS3,378,478 4/1968 Kolodney etal. ..204/195 2\ x',\ Y/X 9/1968Tajirietaluul 104/195 l0/l97l Engelletal ..204/1955 FOREIGN PATENTS ORAPPLICATIONS 2 I ,673 4/1961 Germany ..204/195 Primary Examiner-G. L.Kaplan Attorney-Fred C. Philpitt and Burtan A. Amernick [5 7] ABSTRACTApparatus for the continuous measurement by immersion of oxygencontained in a molten metal which in,- cludes solid oxygen electrolyterod or strip; reference A electrode having known oxygen potential; meansfor measuring the between the reference electrode and the metal whichelectrochemical potential present is to be tested; a protective tubesurrounding the electrolyte; and wherein the electrolyte is held in theend of the tube by means of an oxide cement.

15 Claims, 3 Drawing Figures Fie.3

APPARATUS FOR MEASURING IN A CONTINUOUS MANNER TI-IE OXYGEN IN A MOLTENMETAL The present invention applies more particularly to detection ofthe oxygen potential in copper, lead, tin and silver.

The said apparatus as described in the prior patent applicationcomprises means adapted to measure the potential present between twofaces of a solid electrolyte, one of which is in contact with a phase orphases providing a controlled oxygen pressure or potential used as areference and the other of which is in contact with the molten metalunder test, a tube being provided for protecting the solid electrolyteagainst chemical attacks and against thermal shock and mechanicalstress, which tube closely surrounds the solid electrolyte and forms acontact electrode with the molten metal.

According to the present invention the solid electrolyte which mayconsist of zirconia containing lime or yttria or another material whichconducts solely or primarily by movement of oxygen ions, is shaped inthe form of a rod or of a strip. Preferably, the rod or strip is held inthe end of the protective tube by a cement.

The figure of the accompanying drawings shows an apparatus according tothe present improvement.

FIG. 1 is a longitudinal section.

FIGS. 2 and 3 show details.

The invention will now be described with reference to the accompanyingdrawings.

Two or more rods or strips A A, of solid electrolyte about 3 cm long arecemented into an alumina ring B by means of an oxide cement 6 consistingprimarily for example of alumina, zirconia, magnesia, or other inactiveoxides, which resists penetration of liquid copper and/or gases andwhich does not interfere with the electrical behavior or theelectrolyte.

To the upper ends of the rods or strips A,, A platinum wires 3,4 areattached by winding as shown at l and 2, round the electrolyte rods A A,after the ends have been platinized or sheathed in platinum foil. Thesewires 3, 4 are then led away to the top of the apparatus to be used as aprobe, in twin bore insulators 5 in such a manner that they do not makecontact with one another or with an outer protecting metal or cermettube C.

The upper ends ofthe rods A A, are maintained in a stream or air (asshown by an arrow 8) which enters the cell via a tube D which mayconsist either of a inert oxide refractory or of a stainless steel. Anarrow 9 shows the way along which the air leaves the tube D.

The combined unit A A and B are then cemented into the protective tube Cby, means of a cement 7 which adheres satisfactorily to both of thematerials of B and C. This cement 7 may be electrically conducting anddifferent from that used within the ring B;cements based on alumina,magnesia or alumina mixed with chromium are suitable.

The tube C is extended at its lower end by a tongue E, whose end isdipped in the liquid metal for some time prior to immersion of theprobe, so as to conduct heat from the molten metal to the solidelectrolyte and its surrounding parts, and thus reduce the thermal shockto which these parts are subjected whenthey enter the metal.

The lower ends of the rods or strips of electrolyte A A are fullyimmersed in the liquid copper below the level L of the latter, when thedevice is in use and the emf which is measured is that establishedbetween the upper and lower ends, the actual measurements being madebetween X and Y and X and Y.

The advantage of using rods or strips lie in their cheapness, their goodresistance to thermal shock, and the fact that if the emfs between bothX and Y and X and Y are continuously recorded, agreement between the twoemfs proves that the cell is working properly and that changes in theemfs recorded are caused only by changes in the oxygen potential in thecopper. It might be desirable to have three or more rods or strips andto reject the probe only when two emfs fail to agree.

The alumina ring B may be eliminated if the cement 6 in which theelectrolyte rods A A are set is sufficiently non-conducting, and it isnot affected by being heated over long periods of time in contact withthe cement on the inside of tube C.

The controlled oxygen potential used as a reference may also be amixture of two phases such as a metal and its oxide, as for examplenickel and nickel oxide or copper and cuprous oxide depending on thetemperature.

In such cases, the mixture used as the controlled oxygen potential ismaintained at the upper ends of the solid electrolyte rods A A a gentlestream of deoxidized argon or nitrogen is passed through the cell viatube D, so as to sweep away air which may infiltrate the device.

The mixture W of the two phases metal and its oxide, with a platinumlead 3 (or 4), is held in a hollow in the top of each piece of solidelectrolyte A A (as shown in FIG. 2 or is sintered around the top (asshown in FIG. '3).

What I claim is:

1. Apparatus for the continuous measurement by immersion of oxygencontained in a molten metal which comprises:

a. a solid oxygen electrolyte selected from the group of solid oxygenelectrolyte rod and solid oxygen electrolyte strip and wherein thelength of said electrolyte is greater than the width of saidelectrolyte;

b. one face of said electrolyte being adapted to be contacted with aphase or phases providing a controlled oxygen pressure used as areference;

c. the other face of said electrolyte being adapted to be contacted withthe molten metal which is to be tested;

d. means for measuring the electrochemical potential present between thereference and the metal which is to be tested;

e. the end of the electrolyte which contains the face which is adaptedto be contacted with the phase or phases providing a controlled oxygenpressure is platinized or sheathed in platinum foil and then platinumwire is attached thereto by winding around said end of the electrolyte;and wherein said platinum wire is then led away to the top of theapparatus in such a manner that it does not make contact with the tube;

f. a tube surrounding said electrolyte against chemical attacks, thethermal shock, and mechanical stress due to contact with the liquidmolten metal;

g. said electrolyte is held in the end of said tube by means of a cementwhich adheres satisfactorily to said electrolyte and tube.

2. The apparatus of claim 1 wherein said tube is made of a substanceselected from the group of metal and cermet.

3. Apparatus for the continuous measurement by immersion of oxygencontained in a molten metal which comprises:

a. a solid oxygen electrolyte selected from the group of solid oxygenelectrolyte rod and solid oxygen electrolyte strip and wherein thelength of said electrolyte is greater than the width of saidelectrolyte;

b. one face of said electrolyte being adapted to be contacted with aphase or phases providing a controlled oxygen pressure used as areference;

c. the other face of said electrolyte being adapted to be contacted withthe molten metal which is to be tested;

(1. means for measuring the electrochemical potential present betweenthe reference and the metal which is to be tested;

e. a tube surrounding said electrolyte against chemical attacks, thethermal shock, and mechanical stress due to contact with the liquidmolten metal;

f. said electrolyte is held in the end of said tube by means of cement;and

g. an alumina ring present between said electrolyte and said tube; andwherein said electrolyte is cemented into said alumina ring by means ofan oxide cement which resists penetration of liquid copper, gases andwhich does not interfere with the electrical behavior of theelectrolyte.

4. The apparatus of claim 3 wherein the electrolyte and the ring arecemented into said tube by means of a cement which adheres to both ofthe materials of the alumina ring and the tube.

5. The apparatus of claim 4 in which the cement which adheres to both ofthe materials of the ring and the tube is a substance based on amaterial selected from the group of alumina, magnesia, and alumina mixedwith chromium.

6. The apparatus of claim 3 wherein said oxide cement is selected fromthe group of alumina, zirconia, and magnesia. 1

7. Apparatus for the continuous measurement by immersion of oxygencontained in a molten metal which comprises:

a. at least two solid oxygen electrolytes selected from the group ofsolid oxygen electrolyte rod and slid oxygen electrolyte strip; b. oneface of each of said electrolytes being adapted to be contacted with aphase or phases providing a controlled oxygen pressure used as areference; c. the other face of each of said electrolytes being adaptedto be contacted with the molten metal which is to be tested;

. means for measuring the electrochemical potential present between thereference and the metal which is to be tested;

e. a tube surrounding said electrolytes to protect said solidelectrolytes against chemical attacks, the thermal shock, and mechanicalstress due to contact with the liquid molten metal;

f. said electrolytes are held in the end of said tube by means of acement which adheres satisfactorily to both of said electrolytes andsaid tube.

8. The apparatus of claim 7 wherein an alumina ring is present betweensaid electrolytes and said tube; and

wherein said at least two electrolytes are cemented into said aluminaring by means of an oxide cement which resists penetration of liquidcopper, gases and which does not interfere with the electrical behaviorof the electrolyte.

9. The apparatus of claim 8 wherein the electrolytes and the ring arecemented into said tube by means of a cement which adheres to both ofthe materials of the alumina ring and the tube.

10. The apparatus of claim 9 wherein said cement which adheres to bothof the materials of the ring and tube is a substance based on materialselected from the group of alumina, magnesia, and alumina mixed withchromium.

11. The apparatus of claim 8 wherein said oxide cement is selected fromthe group of alumina, zirconia, and magnesia.

14. The apparatus of claim 7 wherein the ends of said at least twoelectrolytes which contain the faces which are adapted to be contactedwith the phase or phases providing a controlled oxygen pressure areplatinized or sheathed in platinum foil, platinum wires are attachedthereto by winding around said ends of the electrolytes, and theplatinum wires are led away to the top of the apparatus in such a mannerthat they do not make contact with one another or with the tube.

12. The apparatus of claim 7 wherein said phase or phases providing acontrolled oxygen pressure consists of a metal and metal oxide, and islocated at the upper ends of said solid electrolytes.

13. The apparatus of claim 12 wherein platinum wires are fixed to thesolid electrolytes by means of said phase or phases providing acontrolled oxygen pressure and the platinum wires are led away to thetop of the apparatus in such a manner that they do not make contact withone another or with the tube.

15. The apparatus of claim 7 wherein said tube ends in a tongue whichprojects beyond the end of said electrolytes so that it may be used toconduct heat from the molten metal to said electrolytes and itssurrounding parts prior to their immersion in the metal.

1. Apparatus for the continuous measurement by immersion of oxygencontained in a molten metal which comprises: a. a solid oxygenelectrolyte selected from the group of solid oxygen electrolyte rod andsolid oxygen electrolyte strip and wherein the length of saidelectrolyte is greater than the width of said electrolyte; b. one faceof said electrolyte being adapted to be contacted with a phase or phasesproviding a controlled oxygen pressure used as a reference; c. the otherface of said electrolyte being adapted to be contacted with the moltenmetal which is to be tested; d. means for measuring the electrochemicalpotential present between the reference and the metal which is to betested; e. the end of the electrolyte which contains the face which isadapted to be contacted with the phase or phases providing a controlledoxygen pressure is platinized or sheathed in platinum foil and thenplatinum wire is attached thereto by winding around said end of theelectrolyte; and wherein said platinum wire is then led away to the topof the apparatus in such a manner that it does not make contact with thetube; f. a tube surrounding said electrolyte against chemical attacks,the thermal shock, and mechanical stress due to contact with the liquidmolten metal; g. said electrolyte is held in the end of said tube bymeans of a cement which adheres satisfactorily to Said electrolyte andtube.
 2. The apparatus of claim 1 wherein said tube is made of asubstance selected from the group of metal and cermet.
 3. Apparatus forthe continuous measurement by immersion of oxygen contained in a moltenmetal which comprises: a. a solid oxygen electrolyte selected from thegroup of solid oxygen electrolyte rod and solid oxygen electrolyte stripand wherein the length of said electrolyte is greater than the width ofsaid electrolyte; b. one face of said electrolyte being adapted to becontacted with a phase or phases providing a controlled oxygen pressureused as a reference; c. the other face of said electrolyte being adaptedto be contacted with the molten metal which is to be tested; d. meansfor measuring the electrochemical potential present between thereference and the metal which is to be tested; e. a tube surroundingsaid electrolyte against chemical attacks, the thermal shock, andmechanical stress due to contact with the liquid molten metal; f. saidelectrolyte is held in the end of said tube by means of cement; and g.an alumina ring present between said electrolyte and said tube; andwherein said electrolyte is cemented into said alumina ring by means ofan oxide cement which resists penetration of liquid copper, gases andwhich does not interfere with the electrical behavior of theelectrolyte.
 4. The apparatus of claim 3 wherein the electrolyte and thering are cemented into said tube by means of a cement which adheres toboth of the materials of the alumina ring and the tube.
 5. The apparatusof claim 4 in which the cement which adheres to both of the materials ofthe ring and the tube is a substance based on a material selected fromthe group of alumina, magnesia, and alumina mixed with chromium.
 6. Theapparatus of claim 3 wherein said oxide cement is selected from thegroup of alumina, zirconia, and magnesia.
 7. Apparatus for thecontinuous measurement by immersion of oxygen contained in a moltenmetal which comprises: a. at least two solid oxygen electrolytesselected from the group of solid oxygen electrolyte rod and slid oxygenelectrolyte strip; b. one face of each of said electrolytes beingadapted to be contacted with a phase or phases providing a controlledoxygen pressure used as a reference; c. the other face of each of saidelectrolytes being adapted to be contacted with the molten metal whichis to be tested; d. means for measuring the electrochemical potentialpresent between the reference and the metal which is to be tested; e. atube surrounding said electrolytes to protect said solid electrolytesagainst chemical attacks, the thermal shock, and mechanical stress dueto contact with the liquid molten metal; f. said electrolytes are heldin the end of said tube by means of a cement which adheressatisfactorily to both of said electrolytes and said tube.
 8. Theapparatus of claim 7 wherein an alumina ring is present between saidelectrolytes and said tube; and wherein said at least two electrolytesare cemented into said alumina ring by means of an oxide cement whichresists penetration of liquid copper, gases and which does not interferewith the electrical behavior of the electrolyte.
 9. The apparatus ofclaim 8 wherein the electrolytes and the ring are cemented into saidtube by means of a cement which adheres to both of the materials of thealumina ring and the tube.
 10. The apparatus of claim 9 wherein saidcement which adheres to both of the materials of the ring and tube is asubstance based on material selected from the group of alumina,magnesia, and alumina mixed with chromium.
 11. The apparatus of claim 8wherein said oxide cement is selected from the group of alumina,zirconia, and magnesia.
 12. The apparatus of claim 7 wherein said phaseor phases providing a controlled oxygen pressure consists of a metal andmetal oxide, and is located at the upper ends of said solidelectrolytes.
 13. The apparatus of claim 12 wherein platinum wires arefixed to the solid electrolytes by means of said phase or phasesproviding a controlled oxygen pressure and the platinum wires are ledaway to the top of the apparatus in such a manner that they do not makecontact with one another or with the tube.
 14. The apparatus of claim 7wherein the ends of said at least two electrolytes which contain thefaces which are adapted to be contacted with the phase or phasesproviding a controlled oxygen pressure are platinized oR sheathed inplatinum foil, platinum wires are attached thereto by winding aroundsaid ends of the electrolytes, and the platinum wires are led away tothe top of the apparatus in such a manner that they do not make contactwith one another or with the tube.